In conventional flexographic printing operations, it is widely recognized that the consistent delivery of a uniformly thin film of ink to the printing plate is critical to achieving consistent satisfactory print quality and, toward that end, the physical characteristics of the anilox roll largely determine the thinness and uniformity of the ink film transferred to the printing plate. Generally speaking, so long as a minimum acceptable density of ink is consistently maintained, it is desirable that the ink film delivered by the anilox roll be as thin as possible in order to provide optimal contrast and print fidelity.
As is known, anilox rolls are engraved, typically either by a mechanical or a laser engraving operation, to produce an array of recesses circumferentially about the peripheral surface of the roll, commonly referred to as “cells.” Somewhat overly simplified, the principal characteristics of anilox rolls which determine the thickness or thinness of the ink film are the size, shape and depth of each cell, which determine the volume of ink each cell can contain, and the relative arrangement and spacing of the cells over the peripheral roll surface, generally measured and expressed as the number of cells per linear inch of the roll surface and commonly referred to as the “line screen” of a given roll. The engraved volume of the cells of an anilox roll is one of the important factors affecting the color characteristics that will be achieved with a given ink.
In view of these variables in anilox rolls which affect the results in general and the quality in particular of a printing operation, the selection of the appropriate combination of physical characteristics for an anilox roll to accomplish a given printing operation is not necessarily capable of being precisely predicted and, hence, is currently as much an art as a science in actual practice. It is accordingly commonplace to perform test printings with differing anilox rolls preparatory to setting up and implementing a commercial printing operation in order to determine and verify the optimal necessary and desirable roll characteristics, e.g., cell size and shape and line screen, particularly for color testing and matching purposes.
Because of the large size of flexographic printing presses and the anilox rolls used therein, it is difficult, expensive and impractical to perform multiple test runs at the full scale of commercial equipment. Hence, miniature devices commonly referred to as “proofers” have been developed to enable more simplified print testing runs to be performed. While these conventional proofing devices are generally satisfactory in operation at least from the standpoint that the results of such proofers are typically more accurate and reliable than the selection of anilox rolls without preliminary “proofing” tests, the known conventional proofers still suffer various drawbacks and disadvantages. Generally, proofers are of two basic types: proofers adapted for manual operation and proofers that are automated. Manual proofers offer the advantage of portability and operability without access to a utility source, but the results of manual proofing can vary widely according to differences in operator skill, experience and technique, and can even vary in results by the same operator. Automated proofers can offer the advantage of more consistent results, by eliminating operator-induced variations, but are disadvantageous in being more bulky, less portable and requiring access to a utility source for operating power. Thus, there exists a substantial need within the relevant industry for a portable manual proofer which can be operated with precision by different users with consistent results.